mysql使用游标嵌套的两个实例

DELIMITER //

CREATE PROCEDURE ProcessEmployees()
BEGIN
    DECLARE done INT DEFAULT FALSE;
    DECLARE emp_id INT;
    DECLARE emp_name VARCHAR(255);
    DECLARE dept_id INT;
    DECLARE cur1 CURSOR FOR SELECT id, name, department_id FROM employees;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

    OPEN cur1;

    read_loop: LOOP
        FETCH cur1 INTO emp_id, emp_name, dept_id;
        IF done THEN
            LEAVE read_loop;
        END IF;

        -- 嵌套游标处理部门信息
        DECLARE cur2 CURSOR FOR SELECT name FROM departments WHERE id = dept_id;
        DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

        OPEN cur2;

        dept_loop: LOOP
            FETCH cur2 INTO dept_name;
            IF done THEN
                LEAVE dept_loop;
            END IF;

            -- 处理员工和部门的关系
            SELECT CONCAT('Employee: ', emp_name, ' works in Department: ', dept_name);

        END LOOP dept_loop;

        CLOSE cur2;
    END LOOP read_loop;

    CLOSE cur1;
END //

DELIMITER ;

CALL ProcessEmployees();